WASHINGTON  The number of Americans seeking unemployment aid fell to a five-year low last week, a hopeful sign the job market is healing. But much of the decline reflects seasonal volatility in the data.

Weekly unemployment benefit applications fell 37,000 to a seasonally adjusted 335,000, the Labor Department said Thursday. That’s the lowest level since January 2008, just after the recession began.

The four-week average, a less volatile measure, fell to 359,250.

The applications data can be uneven in January. Job cuts typically spike in the second week of the month as retailers, restaurants and other companies lay off temporary workers hired for the winter holidays.

Meanwhile, U.S. builders started work on homes in December at the fastest pace since the summer of 2008 and finished 2012 as their best year for residential construction since the early stages of the housing crisis.

The Commerce Department said Thursday that builders broke ground on houses and apartments at a seasonally adjusted annual rate of 954,000.